Growing concerns over the threat of chemical warfare agents and exposure to toxic industrial chemicals (TIC) have drawn much attention to the challenge of developing new methods for protection against and decomposition of toxic organic materials. Photocatalytic degradation using titanium dioxide (TiO2) is one of the most widely studied methods because it efficiently converts abundant solar energy into effective chemical energy that can be applied to decompose harmful organic materials in air and water. A. Fujishima, K. Honda, Nature 1972, 238, 37; M. Fujihira, Y. Satoh, T. Osa, Nature 1981, 293, 206; P. Sawunyama, A. Fujishima, K. Hashimoto, Langmuir 1999, 15, 3551; K. Nagaveni, G. Sivalingam, M. S. Hegde, G. Madras, Environ. Sci. Technol. 2004, 38, 1600. UV illumination of TiO2 excites electrons from the valence band to the conduction band, leaving holes in the valence band. The electrons then react with oxygen to produce superoxide anions, and the holes react with water to produce hydroxyl radicals. These two species are very reactive and able to decompose a variety of organic toxic chemicals. A. Fujishima, K. Honda, Nature 1972, 238, 37.
However, the photocatalytic degradation of toxic chemicals, including chemical warfare agents, using TiO2 is still challenging in terms of high reaction efficiency with natural sunlight (or mild UV light), immobilization on the supporting materials, and sufficient activity without degradation of the supporting materials. For best photocatalytic activity, a high surface area, anatase crystalline structure of TiO2 is required. Therefore, many researchers have focused on decreasing the particle size and increasing the surface-to-volume ratio of TiO2 to enhance its photocatalytic activity. M. Anpo, T. Shima, S. Kodama, Y. Kubokawa, J. Phys. Chem. 1987, 91, 4305; and S. Y. Chae, M. K. Park, S. K. Lee, T. Y. Kim, S. K. Kim, W. I. Lee, Chem. Mater. 2003, 15, 3326. Fibrous structures of TiO2 have been made by electrospinning of TiO2 precursors from mixed solutions, but there are few reports of depositing well-characterized anatase TiO2 nanoparticles directly onto submicron fibers at room temperature as a post treatment. T. Sugimoto, X. P. Zhou, A. Muramatsu, J. Colloid Interface Sci. 2003, 259, 43; C. Drew, X. Liu, D. Ziegler, X. Y. Wang, F. F. Bruno, J. Whitten, L. A. Samuelson, J. Kumar, Nano Lett. 2003, 3, 143; and D. Li, Y. N. Xia, Nano Lett. 2003, 3, 555. Furthermore, TiO2 fibers prepared using electrospinning from a precursor solution such as titanium alkoxides (Ti(OR)4) with poly(vinyl pyrrolidone) are quite brittle due to their polycrystalline nature, and do not appear to be suitable for photocatalytic applications until after calcination. As a subsequent step, this calcination leads to the formation of anatase TiO2 polycrystalline nanofibers. D. Li, Y. N. Xia, Nano Lett. 2003, 3, 555; and Y. L. Hong, D. M. Li, J. Zheng, G. T. Zou, Nanotechnology 2006, 17, 1986. The brittleness can be overcome by depositing TiO2 on polymeric nanofibers, but it remains a critical challenge to fabricate polymeric nanofibers having high photocatalytic activity without the degradation of polymeric substrates.